Posted By MICHAEL T I forgot to mention that the engine has been involved in a serious fire. MT

Posted By Chris G Hydrofluouric acid could still be present when cooled and would still be a significant hazard given the nature of HF. Look at the MHDS for HF somewhere such as the www.vwr.com website to get an idea of the hazard. Even at a couple of percent concentration serious chemical injuries can occur and treatment is by antidote gel (as 1st Aid) and injections (painful) by a A&E department. Worst case injuries can require amputation or even prove fatal, so treat suspected HF contamination seriously. Also beware that HF and HCl fluoride & chloride sound similar to a tired A&E intern. The treatment for the two though is completely different. Chris

Posted By Jim Walker You can get HF where seals have been burnt (heated in reduced O atmosphere). Known hazard in the scrap car industry -or it should be!! Seriously nasty stuff as you don't get much pain until too late. See http://www.hse.gov.uk/pubns/chindex.htm and then relevant PDF file

Posted By Heather Collins As someone who works in the rubber industry in a company which manufactures viton products, I feel I might know something about this! As Merv says there is little or no risk from handling viton (or other fluoroelastomers - viton is Du Pont's tradename) uncured or cured under normal circumstances. However the curing temperatures used in the industry are not likely to be anywhere near that reach in a fire. Considerable experimentation has been done by those who manufacture these polymers to study the breakdown products at the temperatures reached in a fire. Du Pont certainly publish results of such tests in their product data sheets. They have concluded that HF formation is a definite risk. Therefore I would certainly say that there could still be a residual risk with these O-rings and proper precautions will be necessary. Viton is a relatively expensive polymer and will only be used where high temp/high pressure conditions demand it - O-rings and seals is a typical application - so you will not find it in widespread use. However its use is more common in cars now than it ever has been and the comment above about scrap cars is very relevant.

Posted By John Murgatroyd HUMAN HEALTH EFFECTS OF OVEREXPOSURE TO VINYLIDENE FLUORIDE-HEXAFLUOROPROPENE POLYMER Skin contact with uncured polymer may cause skin irritation with discomfort or rash. Significant skin permeation and systematic toxicity after contact appears unlikely. There are no reports of human sensitization. Eye contact with uncured polymer may cause irritation with discomfort, tearing, or blurring of vision. Inhalation of fumes from burning polymer may cause temporary lung irritation effect with cough, discomfort, difficulty breathing, or shortness of breath. Higher exposures to fumes from burning material may cause pulmonary edema (body fluid in the lungs) with cough, wheezing, abnormal lung sounds possibly progressing to severe shortness of breath and bluish discoloration of the skin. Symptoms may be delayed. Prompt medical attention is required. Smokers should avoid contamination of tobacco products with polymer and should wash their hands before smoking.